#include<string>
#include<iostream>
using namespace std;


int main()
{
	string s1;
	string s2("hello world");
	string s3 = s2;
	cout << s1 << endl;
	cout << s2 << endl;
	cout << s3 << endl;

	string s4("vector stack queue");
	string::iterator it = s4.begin();
	while (it != s4.end())
	{
		cout<<*it<<" ";
		it++;
	}

	for (auto &ele :s4)
	{
		cout << ele << " ";
	}
	return 0;
}